Axial impeller-pump and the like.



F. MARBURG, JR- AXIAL IMPELLER PUMP AND THE LIKE.

APPLICATION FILED MAY 25, 1906.

Patented Dec. 3, 1912.

4 SHEETS-SHEET 1.

Patented Dec. 3, 1912.,

4 SHEETS-SHEET 2.

P. MARB'URG, JR AXIAL IMPELLER PUMP AND THE LIKE.

APPLICATION FILED MAY 25, 1906.

l4 0 7/ I W I V VY//I I LOQGJNQW I. MARBURG, JR. AXIAL IMPELLER PUMP AND THE LIKE.

APPLIOATION FILED MAY 25, 1906.

Patented M03, 1912.

4 SHEETS-SHEET 3.-

33W l was sea I @w/ F. MARBURG, JE- AXIAL IMPELLER PUMP AND THE LIKE.

APPLICATION FILED MAY 25, 1906.

1,@%,99 Patented Dec.3,1912.

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rRANz MAItBURe, 3a., or wIEsBAnE v, GERMANY.

AXIAL IMPELLER-PUMP AND THE LIKE.

Specification of Letters Patent.

Patented Dec.3, 1912.

Application filed May 25, 1906.- Serial No. 318,747.

. ments in Axial Impeller-Pumps and t e Like, of which the following is a specific tion.

This invention relates to axial-flow impeller pumps, blowers, and the like, and its main object is to increase the efficiency and to make the apparatus capable ofoperating against high pressure.

The principal difliculty is to construct a pump of this type in such a manner that the fluid passes through'the impeller, or through the pump, as free as possible from shock and whirling. In an impeller of constant theoretical capacity throughout the impeller, as commonly used at present, great shocks and whirling are experienced at the impeller-inlet, as the actual fluid capacity; consequently the slip, that is the relative backflow within the impeller in the direction of the impeller blades, amounts to fifty per cent. or at very high pressure even to seventy-five per cent. of the theoretical capacity of the impeller.

It is not the object of the present invention to prevent this slip nor even to reduce it, but to take up the slip gradually from the impeller inlet toward the impeller-outlet. At a high peripheral velocity, say from one-hundred to one-hundred and fifty feet per second, which is necessary to produce high pressure, it is essential that the fluid shouldenter into or be drawn into the impeller with a velocity as nearly as possible equal to the theoretical velocity of the axial component of the spiral motion of the inipeller blade, which I will hereinafter term the axial velocity of the impeller-blade, and that the difference between such axialvelocity of the impeller-blade and the corresponding axial velocity of the fluid, which on account of the slip is'unavoidable, should take place only very gradually within the impeller. This result is herein accomplished by constructing the impeller-inlet so small that the theoretical inlet capacity is the same as the actual capacity of the impeller while operating against a given pressure. By increasing the theoretical capacity of the impeller very gradually from twice to four times the theoretical inlet capacity, ccording to different pressures to be produced, a very gradual increase of the slip and of the pressure takes place toward the -impeller outlet. If the unavoidable slip is one-half the theoretical impeller-outlet capacity, then the latter should be twice as great as the theoretical impeller-inlet capacity. If the slip is three-fourths of the theoretical impellensoutlet. capacity, then the latter should be four times as great as the theoretical impeller-inlet capacity.- In other words, the theoretical impeller-inlet capacity should always be the difference between the theoretical outlet capacity and-the un-' avoidable slip. The slip is to be determined by the pressure and by the peripheral ,velocity of the impeller-blades.

To understand more fully the principle of this impeller, it is necessary to state that as the slip, and consequently the difference be at the impeller-outlet.

The purpose of the present invention is to overcome the difficulties set forth above, as will behereinafter set forth with reference to the accompanying drawings, which fully illustrate an embodiment of the invention.

In these drawings :-Figures 1 and 2 are longitudinal axial sections of the pump or device, the former beinga horizontal sec-.

tion and the latter, a vertical section. In Fig. 1 the impellers and diffusers are seen in plan. Fig. 3 is a cross-section at as in Fig. 1; and Fig. 4 is a cross-section at m in Fig. 2. Figs. 5, 6 and 7 are cross-sections of the diffusers taken respectively at lines 00? and a? in Fig. 1.

Inthe drawings, 1 designates the shaft, 2 the main and middle portion of the casing, Q -t'he end-portion of the casing seen at 3 the left in Figs. 1 and 2, and 2 the end-portion of the casing seen at the right in these figures.

two duflusers D and D connected together rigidly, and n'on-rotat-ive in the casing, and

two impellers P and P disposed adjacent thereto in series; but the invention is not limited'to this duplication.

The fluid-inlet 3 is'seen. best in Fig. 1, and the outlet 4 is seen in Fig. 2.

Referring to the principalflviews, the fluid enters the pum at 8, flows first through the rotating impel er P then through the nonrotatingdiifuser D, and thence into the chamber 5; from this chamber it flows by a conduit 6 to the other end of the middle section of the casing-where it enters the other impeller P flows through it to the other ad acent diffuser D through the latter to the central chamber 7, and thence off at the pump outlet 4.

As herein'shown the two diffusers are connected integrally by a sleeve 8, through which the shaft 1 extends. On this sleeve is a hollow hub 9 which fits snugly in the casing and is secured thereto by screws 10, as best seen in Fig. 3. This hub forms a cross partition in the main section 2 of the casing. y

Certain features of the invention shown herein, are only claimed specifically as the same features are claimed more broadly in my former Patent 872,361. v

The core of the impeller has in the present case, a relatively large diameter, which should not be'less than about four-fifths of the corresponding diameter of the outer contour of the impeller-blades'. If the radial width of the impeller-blades is too great in proportion tothe diameter of the said outer contour, a great slip, or even absolute back currents result at the radially inner portions of the blades while the pump operates against high pressure. iThe fluid pressure produced in similar pumps is proportional to the square of-the velocity of the blades .or'of any sections thereof, and as the velocity is least near the axis, the pressure is least near the-axis; therefore w1th a small core-diameter. the fluid will, under certain back pressure, flow backward at the radially inner portions of the impeller-blades, thus causing great loss in the efliciency of the pump. Through higher rotative speed the backflow could be reduced or prevented, but the radially outer portions of the blades would in such a case have too high a-peripheral velocity for the given pressure, whereby losses of a different. nature would occur. Through experiments I have found that for.

a given pressure a certain velocity of the im-i peller-blades gives the best efliciency and I this velocity of said blades can only be approximately reachedby the radially outer as 1 .well as by the radially inner portions of the As shown in the principal views there are of the .diameter of the corresponding outer contour of the impeller-blades.

- A clear distinction must be made between slip,or relative backflow, and absolute backflow. The former reduces thecapacity only but does not cause a. loss in the efliciency of the pump if it be taken up gradually, while the latter constitutes a loss both in the capacity and in the efliciency of the pump.

The drawings also show the gradual increase of the radial .width ofthe impellerblades at the impeller-inlet until they reach their full radial width, and the gradual decrease from their radial width at the impeller-outlet. Theobject'of this feature is also to reduce shock at the impeller-inlet and to reduce suction and whirling at the impeller-outlet. By full radial width. is herein not to beunderstood the maximum radial width of the impeller-blades but only their radial. width at any portion where it reaches in close proximity to the cylinder or'the surrounding wall, which may also be a rotating outer ring.

The purpose and construction of the diffuser will now be explained. In all similar pumps, the fluid under a head, on account of the unavoidable 'slip in the impeller, is carried around with the impeller and has therefore at the impeller-outlet a high peripheral velocity in the direction of the turning motion of the impeller. To utilize this high peripheral velocity of the fluid at the impeller-outlet, or rather the high absolute velocity of which the high rotary velocity and smaller axial velocity are components, a diffuser is employed adjacent to the impeller-outlet. the diffuser, is a gradually increasing capac ity in the direction of the flow of the fluid The characteristic feature of,

and at the same time a gradual deflection of the fluid toward the pump-outlet. The blades of the diflusermust therefore be of opposite angle vor pitchto the blades of the impeller and must be inclined at the angle at which the fluid leaves the impeller, that is in the direction of rotation and at a small angle to the vertical plane through the propeller-axis. The smaller the angle of the impeller-blades the smaller must be the angle of the diffuser-blades; also the angle of the diifuser'blades becomes smaller with greater increase of the theoretical capacity within the impeller. The fluid pressure at the diffuser-outlet, is directly opposed to the motion of the fluid, and as the capacity of the diffuser increases gradually, the velocity of the'fluid will be thereby gradually reduced. The amount of-the kinetic energy which can thus be changed to useful pressure may be calculated by the formula The object of this construction of the diffuser-blades is to permit the fluid to enter more easily into the difluser. Another feature of the diffuser is the shorter blades which are, as shown in the drawing, about half the length of the longer blades and are located toward the outlet end of the diffuser.

These shorter blades may be called aum'liary blades and they serve the purpose of further reducing eddy-currents, while the. longer blades maybe called main blades.

It is self-evident that the impeller as well as the diffuser can have one or more blades and each blade can have part of a turn, or

one or more turns. The producing line of the-blade or blades of the impeller aswell as of the diffuser is not necessarily a line vertical to the axis of the shaft, but may be inclined to the axis; also it could be instead of a straight line a line having any desired curve. In a pump of .this character one or more impellers and diffusers could be used. The construction shown has two impellers operating in series, but a larger number could be employed in series, to produce a higher pressure at a more moderate number of revolutions, which may be desirable in special cases. 7

It is clear that the details of construction of the pump can be changed very much, while the main principles of the invention remain the same e. gradually increasing capacity of both the'impeller and the diffuser combined;

To summarize shortly, the object of the invention is to increase the unavoidable slip gradually from the inlet toward the outlet of the impeller. 'As a consequence the fluid pressure and the high peripheral velocity of the fluid increase gradually withinthe impeller, whereby shocks and eddy-currents are as much as possible prevented. The dif fuser'having gradually increasing capacity, has the purpose to gradually change the kinetic energy of the fluid to useful pres sure.

Obviously the device may be used for receiving and forcing any fluid whether liquid or aeriform.

Having thus described my invention, I claim- Y 1. In an axial impeller ump, an impeller,

and adjacent thereto a di user, the impeller and diffuser having each substantially spiral blades and having each gradually increasing capacity toward its outlet, said increase of the' impeller capacity being produced by a gradual increase of the radial width of said spiral blades toward the impeller outlet.

2. In an axial impeller pump, an impeller, and adjacent thereto a diffuser, the impeller .and diffuser having each substantially spiral blades and having each gradually increasing capacity toward its outlet, said increase of the difluser capacity being produced by a gradual increase of the radial width of said spiral blades toward the diffuser-outlet.

3. In an'axial impeller ump, an impeller,

and adjacent thereto a di user, the impeller and diffuser having each gradually increasing capacity toward its outlet, said increase of the diffuser capacity being produced by a gradual increase of the radial width and of the angle or pitch combined of said spiral blades, toward the difluser outlet.

4. .In an axial impeller pump, an impeller, and adjacent thereto a difluser, the impeller and difl'user having each substantially spiral blades and having each radually increasing capacity toward its out et, said increase of the capacity being produced in each' by a gradual increase .of the radial width of the spiral blades toward its outlet.

5. In an axial impeller pump, an impeller, I and adjacent thereto a diffuser, the impeller and diffuser having each substantially spiral I blades and having each gradually increasing capacity towardits outlet, said increase of the capacity being produced within the impeller by a gradual increaseof the radial width of the spiral blades toward the impeller-outlet and said increase of the capacity being produced within the difluser by a gradual increase of the radial width and the pitch combined of the spiral blades toward thedifluser-outletQ 6. In an axial impeller pump, an impeller, and adjacent thereto a diffuser, the. impeller and diffuser having each substantially spiral blades and having each gradually increasing capacity toward its outlet, the angle or pitch of the difi'user-blades being opposite or reverse to the angle or pitch of the impeller blades, the latter increasing gradually to theirfull radial width at the impeller outlet substantially spiral bladcs,-and having each I gradually increasing capacity toward the outlet, the angle or pitch of the diffuser blades being opposite or reverse to the angle or pitch of the impeller blades, said impeller blades and difiuser blades having their greatest radial diameter at their end approaching the outlet, said impeller blades and difi'user blades gradually decreasing in their radial width in a direction toward the inlet.

8. In an axial impeller pump, an impeller,

pitch of the diffuser-blades being opposite or reverse to the angle or pitch of the impellerblades, the diffuser-blades increasing gradually to their full radial width at the diffuser outlet.

In testimony whereof I atfix my signature in presence of two witnesses.

' FRANZ MARBURG, J UN. Witnesses:

'RicnAnp MARBURG, WALTER Hi'iusme, 

